The development and formulation of effervescent compositions has traditionally been focussed on the use of various constituents for obtaining in situ chemical reactions upon contact with water, so as to form a gas to provide effervescent action.
This type of acid/base reaction systems has for instance been disclosed in U.S. Pat. Nos. 4,180,467, 4,406,708, and 4,436,720. The cleansing benefit derived from the effervescent action has been well documented in these prior art patent documents.
Furthermore, it is known in the art that effervescent action can be applied for promoting rapid release of detergents into the wash liquor so as to provide favourable cleaning performance. In this connection, several solution involving effervescent systems have been proposed to try and avoid problems of poor dissolution and dispensing behaviour.
For example, in WO-98/04671 effervescent systems for use in detergents are disclosed in which, in an effort to improve dissolution, acid and alkaline reactants which react upon contact with water to produce a gas, are mixed with a stabilising agent, so as to produce a substantially anhydrous effervescent particle for use in a washing cycle. Similarly, WO-98/35011 discloses particles comprising sodium bicarbonate and organic acid reactants which react together and which are formed into a particle by using a binder.
Furthermore, EP-A-918,087 refers to co-builder particles for use as additive in detergent compositions, comprising bicarbonate and polycarboxylic acid which are formed by roller compaction and which contain no free moisture.
Another way of providing effervescent action is disclosed in U.S. Pat. No. 3,947,567. In this document, a method of providing an effervescent mouth wash is disclosed, wherein a liquefied gas is distributed under pressure in an aerosol dispensing container.
WO-86/02832 discloses yet another way to provide effervescence to anhydrous compositions when these are contacted with water. In this document, effervescent compositions are disclosed, comprising an essentially anhydrous base medium and inorganic oxide material containing an adsorbed gas, e.g. carbon dioxide. This gas may be any gas capable of being adsorbed by the inorganic oxide material in sufficient amounts to provide effervescent action upon contact with water.
However, the technology applied in the above-described effervescent systems cannot be used for aqueous liquid cleaning compositions without incurring considerable problems. A main reason is that incorporation of reactants which react on contact with water to produce a gas, into such an aqueous liquid would lead to immediate reaction and that this immediate reaction can only be avoided by segregating these reactants, e.g. by encapsulating them, which would entail considerable cost. Furthermore, the technology disclosed in U.S. Pat. No. 3,947,567 and WO-86/02832 cannot be suitably used in aqueous cleaning systems.
It follows that there is still a need for providing an effervescent aqueous liquid cleaning composition especially for use in fabric washing, which produces adequate effervescent action when contacted with water and of which the manufacturing cost is moderate.
Consequently, an object of the present invention is to provide such an effervescent aqueous liquid cleaning composition.
It is another object of the invention to provide an effervescent aqueous liquid cleaning composition which is easy to produce at affordable cost and which gives a consumer perceivable benefits.
It has now surprisingly been found that these and other objects can be achieved when applying the effervescent aqueous cleaning composition of the present invention.